News

Aug 31, 2012

Energy secrets of the Passive House can help you save

In the 1970s, an experimental house was designed and built in Saskatchewan. Driven by the energy crisis of the time, and funded by grants, a group of scientists tried to build a house that could survive the prairie winter and use as little energy as possible.

They called it the Saskatchewan Conservation House, and the Regina home is still in use, 35 years later.

Canadians were top of the world in energy conservation in the 1970s, says Jacob Rodgers, a sustainable building advisor and contractor with J.Norris Construction. But when energy prices dropped, and funding dried up, Rodgers says all of that research and learning was abandoned.

Ten years later, a German physicist named Wolfgang Feist took some of the ideas from Saskatchewan Conservation Home and incorporated them into modelling software he was developing. Feist was interested in ultra-efficient home construction, and his software, still used today, can accurately predict energy usage for a building before construction begins.

Feist established a certification process under the banner of Passivhaus Institut. Rodgers, a member of the Canadian Passive House Institute, has three projects on the go at the moment: two laneway homes in Vancouver's Strathcona neighbourhood, and a larger home in Belcarra. While none of the projects will be certified to the Passive house standard, Rodgers is incorporating many of its principles in the construction.

Conserve first, generate later

A certified Passive home requires very little energy, even on the coldest of winter days, says Rodgers. Passive homes reduce the amount of energy needed for heating — by far the biggest energy cost in a residence — by 90 per cent.

By constructing homes to be so energy efficient, it's much easier to make them net zero energy homes by adding onsite renewable energy generation. It's possible because the energy demands of such houses are so low.

"We've been building leaky buildings to allow for air flow," says Rodgers. "But in addition to that leading to wasted energy, it also leads to condensation, moisture and mould, resulting from hot air meeting cold air."

A Passive House deals with that problem by being air tight. So tight, says Rodgers, that heat-recovery ventilators (HRVs) are necessary to provide those in the house with appropriate ventilation while minimizing energy requirements.

HRVs are responsible for exhausting stale air from inside — mostly from kitchens and bathrooms — and bringing in fresh air from outside. These devices are able to allow for the heat energy to pass from one stream to the other, so in the winter, the air from inside warms up the cool air from outside as it enters the house.

It's anticipated that the next B.C. Building Code — expected to be in place by late 2013 — will specify that all new houses meet or exceed minimum standards for energy efficiency as prescribed in the proposed National Energy Code for Houses (NECH). It's also expected that the NECH will encourage the use of heat recovery ventilation systems.

Constructing a Passive house costs more, estimated at 5 to 12 per cent more than a regular home. But Rodgers says traditional, shorter-term thinking related to the costs of building construction doesn't make sense in the context of a structure that will last for a minimum 20 years.

That extra cost of construction is more than made up by the energy savings — even with B.C.'s comparatively affordable electricity prices — over the life span of a house.

Energy efficiency through home renovations

Not many people are building their home from the ground up. But Rodgers says the following three Passive House principles can be incorporated into basic home renovations.

Replace windows: Old windows are about as useful as a layer of cellophane, says Rodgers.

Add exterior insulation: Exterior insulation can reduce air leakage by sealing the holes in the wood-framed wall. New materials like rock wool, waste material from quarries that is a common, fire-safe insulator in Norway, are improving the effectiveness. "Insulation," says Rodgers, "is not sexy, but it's key to the Passive House philosophy. Most Passive homes, he says, have walls that are 12 to 14 inches thick."

Install a heat recovery ventilator: It's possible, says Rodgers, to install an HRV as a retrofit. Some models have dehumidifiers built in, so they are doubly effective.

A building scientist at home

Rodgers stresses that every project he takes on demands that he do research to determine the best approach. He also has to stay current with new technologies and materials. That's why he thinks of himself as a building scientist.

He hopes to soon become a certified Passive House builder. To do that he just has to build a certified Passive House. He's got the design, the land and the client.